Method of forming a dental appliance

ABSTRACT

The present disclosure includes dental appliances and methods of making and using such appliances. One method for forming a dental appliance includes forming a liquid thermoset polymer material into a semi-solid first shape, thermoforming the semi-solid first shape of thermoset polymer material onto a dentition mold, and curing the thermoset polymer on the dentition mold with a curative trigger to complete a molecular cross-linking reaction.

BACKGROUND

The present disclosure is related generally to the field of dentaltreatment. More particularly, the present disclosure is related to thefabrication of polymeric dental appliances for orthodontic dentaltreatment.

Many dental treatments involve repositioning misaligned teeth andchanging bite configurations for improved cosmetic appearance and dentalfunction. Repositioning can be accomplished, for example, by applyingcontrolled forces to one or more teeth over a period of time.Repositioning teeth for aesthetic or other reasons has been accomplishedby wearing what are commonly referred to as “braces.” Braces typicallyencompass a variety of hardware such as brackets, archwires, ligatures,and O-rings.

Some dental processes use polymeric dental positioning appliances,rather than braces, for realigning teeth. Such appliances may, forexample, utilize a thin shell of material having resilient properties,referred to as an “aligner” that generally conforms to a patient's teethbut is slightly out of alignment with the present (e.g., initial) toothconfiguration. Placement of such an appliance over the teeth providescontrolled forces in specific locations to gradually move the teeth intoa new configuration. Repetition of this process with successiveappliances that provide progressive configurations eventually move theteeth through a series of intermediate arrangements to a final desiredarrangement.

Many processes for forming such dental appliances utilize thermoplasticmaterial. These materials have a long period in which the forming of thedental appliance can take place, and therefore are desirable materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a jaw including patient's teeth and an embodiment ofa dental appliance to treat a dental condition of the patient accordingto the present disclosure.

FIG. 1B illustrates a dental appliance cross section as taken along line1B-1B of FIG. 1A.

FIG. 1C illustrates a dental appliance cross section as taken along line1C-1C of FIG. 1A.

FIG. 2A is a block diagram illustrating a method for fabricating adental appliance according to an embodiment of the present disclosure.

FIG. 2B is a block diagram illustrating another method embodiment forfabricating a dental appliance according to the present disclosure.

FIG. 3 illustrates an embodiment of a first shape with respect to adentition according to the present disclosure.

FIG. 4A illustrates an embodiment of a first shape substantiallyhorseshoe-shaped in at least one dimension according to the presentdisclosure.

FIG. 4B illustrates a first shape cross section as taken along line4B-4B of FIG. 4A.

FIG. 5A illustrates an embodiment of a first shape substantiallyhorseshoe-shaped in at least two dimensions according to the presentdisclosure.

FIG. 5B illustrates a first shape cross section as taken along line5B-5B of FIG. 5A.

FIG. 6 illustrates an embodiment of a first shape having a variablethickness according to the present disclosure.

FIG. 7 illustrates working range curves of displacement as a function ofstatic force for a thermoset polymer material in contrast to athermoplastic material that may be used to form dental appliances ofembodiments according to the present disclosure.

FIG. 8 illustrates stress relaxation performance curves of percentage ofload remaining as a function of time for a thermoset polymer material incontrast to a thermoplastic material that may be used to form dentalappliances of embodiments according to the present disclosure.

FIG. 9 illustrates a computing device embodiment to perform a method forevaluating a dental condition according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure provide dental appliances andmethods of making and using such appliances. In various embodiments, forexample, a method embodiment for forming a dental appliance is describedthat includes partially curing a thermoset polymer material into aformable first shape. This method embodiment further includesthermoforming the first shape of thermoset polymer material onto adentition mold, and fully curing the thermoset polymer on the dentitionmold to complete a molecular cross-linking reaction.

In various embodiments, a dentition of the patient's teeth can be formedin a number of ways. For example, an impression of the patient's teethcan be taken to form the dentition.

In some instances, one or more digital models can be created and used toform the dentition. For example, the patient's teeth or the dentitioncreated from the patient's teeth can be digitally scanned and the datamanipulated to form dentitions used for repositioning teeth or forapplication of materials (e.g., chemical treatments) to the patient'steeth.

For instance, a digital model can be used to fabricate a dentalappliance corresponding to a present, anticipated, and/or desiredconfiguration of the patient's dentition through analysis and/ormanipulation of the data set forming the digital model. Additionaldetail on the use of digital modeling can be found in commonly assignedU.S. patent application Ser. No. 12/283,770, filed on Sep. 16, 2008,entitled “Dental Condition Evaluation and Treatment”.

A series of dental appliances, e.g., “aligners,” generally rely ondesigning and fabricating some, most, or all of the appliances, to beworn by the patient over time, at the outset of treatment, or whiletreatment is occurring. In some processes, the design of the appliancesuses computer modeling of a series of successive tooth arrangements andthe individual appliances are designed to be worn over the teeth and toreposition the teeth by using the appliances in a serial order,progressing from a first appliance, through each of the intermediateappliances, to the last appliance. An example of a dental treatmentsystem, including a series of dental appliances, e.g., “aligners,” isdescribed in commonly-assigned U.S. Pat. No. 5,975,893, which isincorporated herein in its entirety.

Dental aligners have been made of thermoplastic polymers, since thiscategory of polymer can be easily thermoformed into a desired alignerconfiguration. For example, a sheet of thermoplastic polymer materialcan be heated over a mold in order to conform the thermoplastic polymermaterial to the shape of the mold. The mold may be of an existingconfiguration of a patient's teeth, or of an intended futureconfiguration.

However, in some implementations, thermoplastic polymer materials tendto fatigue over time, particularly under constant loading, such as inorthodontic treatment applications. Thermoplastic polymer materials mayalso tend to deform over time due to stress relaxation of material,and/or material fatigue in some instances.

In some applications, aligner deformation can reduce force delivered tothe teeth for some orthodontic movements, and thus, can provideinconsistent application of force throughout a particular course oftreatment with a given aligner. In such applications, the fatigue and/ordeformation limitations associated with thermoplastic polymer materialsmay limit the magnitude of movement that can be obtained from aparticular aligner, or the time over which a particular aligner may beutilized.

In the embodiments described in the present disclosure, aligners can bemolded using a thermoset polymer material. As used herein, a thermosetpolymer material includes those polymeric materials that once shaped byapplied energy (e.g., heat, pressure, radiation), or chemical reaction,so as to form a cross-linked polymeric matrix, are incapable of beingreprocessed into a different form by further application of theparticular energy.

That is, aligners can be molded using a category of polymers that areirreversibly cured in the desired aligner configuration. Examples ofthermoset polymer materials include castable/casting polyurethane,acrylate curable polymers, silicone thermoset polymers and elastomers,and epoxy polymers, among others.

An aligner is formed to a patient's teeth, or to programmed dentitions(e.g., intermediate teeth configurations of a proposed orthodontictreatment plan). An aligner formed using thermoset polymer materials iscapable of capturing the details of a particular dentition, either byintermediate thermoforming over the dentition, or by another suitableprocess. Several examples of methods for forming a dental appliance(e.g., an aligner) using thermoset polymer materials are provided below.

FIG. 1A illustrates a jaw including patient's teeth and an embodiment ofa dental appliance to treat a dental condition of the patient accordingto the present disclosure. The devices, methods, or systems of thepresent disclosure can be, or employ, any manner of positioners, trays,retainers, and/or other removable dental appliances. The systems for usein various embodiments of the present disclosure can utilize a singleappliance, or a plurality of such appliances that can, for example, beworn by a patient successively in order to achieve the gradual toothrepositioning, as described herein.

Accordingly, embodiments of the present disclosure are not limited to an“aligner” that is intentionally fabricated slightly out of alignmentwith the present tooth configuration so as to provide force to one ormore teeth. As will be appreciated, a dental appliance according toembodiments of the present disclosure may conform to a patient's toothconfiguration. Thus, according to at least one embodiment of the presentdisclosure, treatment targeted at a particular tooth, several teeth,and/or the gingiva can be accomplished concurrent with alignmenttreatment (e.g., tooth position adjustment), or separate and distinctfrom the alignment treatment.

The present disclosure also includes one or more method embodiments forforming (e.g., casting) a dental appliance. For example, one such methodembodiment includes delivering a fluid (e.g., liquid, viscous mass)thermoset polymer precursor to a first mold having an internal cavity.

The internal cavity has a surface corresponding to an external surfaceof the dental appliance. The method further includes placing a secondmold in proximity to the first mold such that a volume for the thermosetpolymer precursor remains therebetween, the second mold being a positivedentition mold having an external surface corresponding to an internalsurface of the dental appliance, and curing the thermoset polymerprecursor with energy to complete a molecular cross-linking reaction,e.g., cause molecules of the thermoset polymer precursor to irreversiblylink into a rigid three dimensional structure.

In various apparatus embodiments, a tooth position adjustment dentalappliance is produced according to a method set forth above, the dentalappliance having cavities shaped to receive and resiliently repositionteeth from a first arrangement to a second arrangement. For example, adental appliance can include a shell having a number of cavities toreceive one or more teeth formed of cross-linked polymer materials. Insome embodiments, the shell is formed of thermoset polymer materials.

In one or more apparatus embodiments, the dental appliance is an aligner(e.g., shell) having a number of cavities to receive one or more teeth.The aligner is one of a series of aligners corresponding to intermediatesteps of an orthodontic treatment where the number of cavities arearranged to reposition the one or more teeth from a first configurationto a successive configuration, and the aligner is fabricated frommaterial that is irreversibly cured to irreversibly link molecules intoa rigid three dimensional structure.

A dental appliance 106 (e.g., a dental positioning appliance such as analigner, a tray for delivery of chemicals in proximity to the teeth orgums, etc.) can include a number of cavities for receiving one or morecorresponding teeth. In various embodiments, the cavities can correspondto one, or multiple, teeth, implants, and/or other features of apatient's jaw.

Embodiments of the present disclosure include dental appliances, such asaligners for orthodontic positioning of one or more teeth, formed fromthermoset polymer materials. In contrast to thermoplastics, thermosetpolymer materials tend to fatigue less over time when placed underconstant loading, such as in orthodontic treatment applications.Thermoset polymer materials deform less over time due to stressrelaxation of material, and material fatigue, thereby maintaining theforce delivered to the teeth for orthodontic movements for a longerperiod, and providing more consistent application of force throughout aparticular course of treatment.

Embodiments of the present disclosure are described in relation to theaccompanying drawings, which will at least assist in illustrating thevarious features of the various embodiments. In the Figures, the firstdigit of a reference number refers to the Figure in which it is used,while the remaining two digits of the reference number refer to the sameor equivalent parts of embodiment(s) of the present disclosure usedthroughout the several figures of the drawing. The scaling of thefigures does not represent precise dimensions and/or dimensional ratiosof the various elements illustrated herein.

The dental appliance 106 may be designed to fit over a number of, inmany instances all teeth, present in an upper or lower jaw. Dentalappliances can be configured to apply force to reposition one or moreteeth from a first configuration of the teeth to a successiveconfiguration of the teeth, used in application of medication or otherbeneficial materials in proximity to one or more teeth and/or the gums,or used to hold teeth in place, among other such uses.

In some embodiments, certain individual teeth, or small sets of theteeth, can be repositioned while one or more other the teeth provide abase or anchor region for holding the repositioning appliance in placeas it applies a resilient repositioning force against the tooth or teethto be repositioned. Some embodiments can have repositioning portions,anchor portions, and/or portions that cover a portion of a tooth orteeth but do not provide any force to the covered tooth or teeth.

In various embodiments, one or more cavities of the dental appliance areformed in an oversized manner with respect to the teeth over which it isto be applied (e.g., by scaling-up) for chemically treating one or morecertain teeth. For example, one or more chemicals (e.g., medications) orother materials may be applied to the interior surface of the appliancedue to the scaled up nature of this appliance's fabrication.

FIG. 1B illustrates a dental appliance cross section 112, as taken alongline 1B-1B of FIG. 1A. FIG. 1C illustrates a dental appliance crosssection 118, as taken along line 1C-1C of FIG. 1A. As illustrated, thedental appliance can have a U-shaped cross-section to form one or morecavities for placement of a patient's teeth therein. Such a shape can beformed, for example, by placement of a partially cured thermoset polymermaterial over a dentition mold (e.g., forming the inner surface).

Thermoset polymer material can be classified as uncured, partiallycured, or cured (i.e., fully cured). Uncured thermoset polymer materialdescribes unreacted resin (e.g., A-stage of cure). Fully cured thermosetpolymer material describes thermoset polymer material having completemolecular cross-linking reaction, so as to irreversibly cross-linkmolecules into a rigid three dimensional structure (e.g., C-stage ofcure). Partially cured thermoset polymer material describes thermosetpolymer material between uncured and fully cured stages of cure (e.g.,sometimes called the green phase or B-stage of cure).

FIG. 2A is a block diagram illustrating a method for fabricating adental appliance according to an embodiment of the present disclosure.According to one or more embodiments, a method for forming a dentalappliance includes forming and partially curing a liquid thermosetpolymer material into a semi-solid first shape at 220. The methodfurther includes thermoforming the semi-solid first shape of thermosetpolymer material onto a dentition mold at 222, and curing the thermosetpolymer on the dentition mold with energy, or chemical reaction, tocomplete a molecular cross-linking reaction at 224.

A wide range of processing techniques may be used for forming, orpartially curing, the liquid thermoset polymer material into asemi-solid first shape, including molding, extrusion, rolling, etc. Somesuitable processing techniques for producing the first shape includecompression molding, such as is used to make precision parts; liquidinjection molding, for example using low pressure in conjunction with abottom fill mold; and reaction injection molding with high pressureimpingement mixing. Other suitable processing techniques may also beused, including, but not limited to: open casting; centrifugal molding,including pipelining, making of sheet goods and use of multi-cavitymolds; ribbon flow moldless casting where the first shape is formedusing rollers rather than a mold; transfer molding, such as is used tomake multiple precision parts; rotational molding, often used to makehollow items; vacuum casting, as may be used to make wire or fiberinserts; pressure casting utilizing a pressure chamber; B-staging usedwhen the shape of particular molds create difficulty in holding liquids;spray; solvent casting involving low pressure for fabric penetration;and dipping for materials having a sufficiently long working life whichmay be heat activated; among others.

FIG. 2B is a block diagram illustrating another method embodiment forfabricating a dental appliance according to the present disclosure.According to one or more embodiments, a method for forming a dentalappliance includes delivering a fluid thermoset polymer precursor to afirst mold (e.g., to form a sheet or shell, for example) at 226,partially curing the thermoset polymer precursor in the first mold at228, removing the partially cured thermoset polymer precursor in asemi-solid state from the first mold at 230, thermoforming the partiallycured thermoset polymer precursor onto a dentition mold at 232, andcuring the thermoset polymer precursor on the dentition mold with energyto induce a cross-linking reaction at 234.

One example of a method embodiment such as that described in FIG. 2Bincludes two or more urethane prepolymer components being prepared andmixed with one or more curatives to initiate a chemical reaction of theurethane prepolymer components. The thermoset polymer precursor is cast,or molded, into a preliminary configuration (e.g., sheet, shell), andpartially cured.

As the thermoset polymer precursor begins to solidify into thermosetpolymer material, but while the sheet is still not fully cured (e.g., asemi-solid state), it is often referred to as being in a “green” phase.The green phase sheets may be removed from the cast, or mold, and usedto fabricate a dental appliance (e.g., an aligner) such as bythermoforming the green phase sheet onto a negative dentition mold ofthe intended configuration (e.g., 104 in FIG. 1A). Thereafter (e.g.,after forming into an aligner configuration), the dental appliance canbe further (e.g., fully) cured.

In some embodiments, the dental appliance is formed using green phasematerial that is further cured by exposure to a curative trigger. Thecurative trigger can be one or more of energy (e.g., light, heat,radiation), force (e.g., pressure), or chemical reaction. After forming(e.g., applied to a mold), the green phase material can be exposed tothe curative trigger for some period of time to allow the formed dentalappliance to substantially cure as a thermoset polymer material.However, embodiments of the present disclosure are not limited toexposing the green phase material to a curative trigger after forming inorder to obtain substantial curing.

In some embodiments, a dental appliance may be formed after exposure ofthe green phase material to a curative trigger (e.g., at an appropriatetime during curing as the thermoset polymer precursor transitions tobeing substantially cured as a thermoset polymer material). That is,curing may be initiated as a result of a chemical reaction, and at somewindow of time during the curing process, the partially cured materialsare removed from a preliminary configuration mold, thermoformed onto adentition, and allowed to continue curing thereon, without furtherexposure to a curative trigger (e.g., energy, force, chemical, or othertrigger).

According to one or more embodiments, a method for forming a dentalappliance does not include forming green phase stock used for furtherforming into a dental appliance. Rather, a dental appliance isfabricated directly from the thermoset polymer precursor materials.

For example, curable polymers can be mixed with the desired componentsand initiators. This thermoset polymer precursor can then be directlyinjected into a positive dentition mold, and allowed to partially curein the mold.

In this manner, a partially cured dental appliance can be formeddirectly. This partially cured dental appliance aligner can be furthercured (e.g., fully), in the mold or after removal from the mold, byapplication of energy such as radiation, light, heat, pressure, or somecombination thereof, to complete the cross-linking reaction. Again,further curing is not limited by input of additional energy, and canalso occur without additional application of additional energy or othercurative trigger (e.g., force).

In some embodiments, the dental appliance can be molded of a thermosetpolymer material, as discussed herein. As will be appreciated, thedental appliance can be placed within a molding tool and the thermosetpolymer precursor can be supplied to the molding tool to form the dentalappliance. Supplying the thermoset polymer precursor can, for example,include injecting a fluid thermoset polymer precursor, and an optionalcatalyst, into the mold under low pressure to fill the mold cavityvolume.

Since the thermoset polymer precursor can have a low viscosity, thethermoset polymer precursor can substantially fill spaces defined byvarious surfaces of the dental appliance. A curative trigger (e.g.,pressure, one or more chemicals, light and/or heat that causes thethermoset polymer to finally cure) can then be applied to cure thethermoset polymer precursor to form the dental appliance.

In some embodiments, a method for molding a dental appliance includesplacing a mold having an internal cavity, where the internal cavityincludes a first portion and a second portion, at a first position sothat the second portion is in a higher relative position than the firstportion. Also, a thermoset polymer precursor can be injected through themold into the first portion of the internal cavity to partially fill theinternal cavity.

Once the thermoset polymer precursor has been injected, the mold can bemoved from a first position to a second position to reorient the firstportion and the second portion so the first portion is in a higherrelative position than the second portion. The thermoset polymerprecursor can then be injected through the mold into the second portionof the internal cavity to at least partially fill the internal cavity.

After partial or substantially complete curing, the dental appliance canbe removed from the mold. A post cure process can also be used.

As will be appreciated, a variety of molding processes exist that can beused to form the dental appliances. Examples of such molding processescan include thermoset polymer precursor transfer molding, compressionmolding, and injection molding, among others.

In various embodiments, the dental appliance could be formed in acasting process or stamping process. In one or more embodiments,portions (e.g., layers, sections) of a dental appliance can beindividually formed (e.g., cast, molded) and subsequently coupledtogether to form the dental appliance. Examples of suitable techniquesfor coupling the individual portions include use of natural or syntheticadhesives and/or thermal energy to join the individual portionstogether.

As provided herein, thermoset polymer materials can be formed from thecross-linking (e.g., polymerization) of one or more thermoset polymerprecursor(s). In the embodiments described herein, the thermoset polymerprecursor can be selected from an unsaturated polyester, a polyurethane,an epoxy, an epoxy vinyl ester, a phenolic, a silicone, an alkyd, anallylic, a vinyl ester, a furan, a polyimide, a cyanate ester, abismaleimide, a polybutadiene, and a polyetheramide, among othersuitable thermoset polymer materials. In one embodiment, the thermosetpolymer precursor includes resin in an A-stage of cure (i.e., unreactedresin).

As will be appreciated, the thermoset polymer material used in theembodiments of the present disclosure can also include reinforcementmaterials and/or additives such as one or more fillers, wires, fibers,curing agents, inhibitors, catalysts, and toughening agents (e.g.,elastomers), among others, to achieve a desirable combination ofphysical, mechanical, chemical, and/or thermal properties. Reinforcementmaterials can include woven and/or nonwoven fibrous materials,particulate materials, and/or other high strength materials. Examples ofreinforcement materials can include, but are not limited to, syntheticfibers, natural fibers, and ceramic fibers. Fillers include materialsadded to the matrix of the thermoset polymer material to alter itsphysical, mechanical, thermal, or chemical properties. Such fillers caninclude, but are not limited to, organic and inorganic materials, clays,silicates, mica, talcs, rubbers, fines, and paper, among others.

In one or more embodiments, the classes of thermoset polymer materialsare biocompatible (e.g., thermoset polyurethanes, silicone rubbers, andacrylics such as methyl methacrylate (MMA) and polyethene glycoldimethacrylate (PEGDMA) copolymer). Embodiments can use a material thatis mechanically and/or chemically stable in a saliva environment. Insome embodiments, it is beneficial for the thermoset polymer material tobe chemically resistant to teeth cleaning materials.

As will be appreciated, the thermoset polymer precursor can be formedinto the thermoset polymer material by a polymerization reactioninitiated and cured through heat, pressure, chemical reaction withcatalysts, ultraviolet light, irradiation (e.g., electron beamprocessing), and/or other types of energy. The curing process transformsthe thermoset polymer precursor into the thermoset polymer by across-linking process.

Energy or catalysts may be added that cause the molecules to react atchemically active sites, linking the molecules into a rigidthree-dimensional structure. The cross-linking process forms a moleculewith a relatively larger molecular weight, resulting in a materialhaving a higher melting point. The polymerization reaction increases themolecular weight such that the material solidifies, and will burn ratherthan melt at elevated temperatures.

In one or more embodiments, the thermoset polymer material of thepresent disclosure can have at least one percent (1%) cross-linkingnetwork structure. This improves the structural characteristics of thematerial for a dental appliance application in some instances, asdiscussed further below.

The thermoset polymer material can have clarity characteristics rangingfrom opaque to clear (e.g., transparent). The thermoset polymer materialcan be non-colored or colored (e.g., include colored agents), whichthereby may provide shading ranging from a colored opaque to a tintedtransparent, or further to a clear transparent.

As previously discussed, polymeric dental positioning appliances can beused for aligning teeth. Such appliances may, for example, utilize athin shell of material having resilient properties that generallyconforms to a patient's teeth but is slightly out of alignment with thepatient's teeth. Placement of such an appliance over the teeth providescontrolled forces in specific locations to gradually move the teeth intoa new configuration.

Therefore, the material used to fabricate the polymeric dentalpositioning appliances (e.g., an aligner) needs to have a tensilestrength such that when the material is deformed over an initial toothconfiguration, sufficient force may be transferred to the tooth, orteeth, causing the deformation. Since deformation of the polymericdental positioning appliance is used to create the forces applied to atooth, or teeth, the material should be capable of elongation withoutbreakage, have sufficiently large tensile and flexural moduli, and/orhave stress relaxation characteristics that allow for the generation offorce by resilient opposition to deformation.

In one or more embodiments, the thermoset polymer material can have oneor more of the following characteristics: a tensile strength at yield ofgreater than 6,000 pounds per square inch (psi), an elongation at yieldof greater than ten percent (10%), an elongation at break of greaterthan eighty percent (80%), a tensile modulus at secant one percent (1%)greater than 100,000 psi, a flexural modulus greater than 100,000 psi,and stress relaxation in 37° C. and one hundred percent (100%) relativehumidity over 24 hours of more than twenty percent (20%).

Dental appliances fabricated using thermoset polymer material, such asthose having one or more of the above-mentioned characteristics, can bemore resilient than that of thermoplastic polymers. Due to thecross-linked structure, thermoset polymer materials can retain theiroriginal shape better and/or longer than thermoplastic polymers, andthereby maintain application of a relatively more consistent force whenused to achieve orthodontic tooth movement. As will be appreciated,fabricating dental appliances using thermoset polymer materials thatretain their original shape better and/or longer can improve dentalappliance performance, such as over a given treatment time of aparticular dental appliance (e.g., 2-3 weeks for some alignerembodiments), since material fatigue is reduced.

Less material fatigue results, for example, in a more constant forcebeing delivered by a dental appliance formed with a thermoset polymermaterial. Using a dental appliance fabricated of thermoset polymermaterial for orthodontic treatment can also result in more predictableoutcomes (e.g., teeth movement) with respect to original programmedmovements in some instances. Increasing predictability through bettercontrolled force application can reduce treating professionalintervention to correct a teeth configuration that does not matchexpected results.

Improved performance can also support longer treatment periods and/orgreater tooth movement distance, and thus, fewer intermediate alignersbetween an initial and final teeth position, may be utilized in someinstances. In turn, fabrication costs may be reduced for some treatmentplans, since fewer dental appliances may be needed.

FIG. 3 illustrates an embodiment of a first shape 343 with respect to adentition 344 according to the present disclosure. According to one ormore embodiments, the first shape 343 can be formed to be substantiallyflat, such as into a semi-solid sheet of partially cured thermosetpolymer material, for example.

The first shape 343 can be formed to have a substantially constantthickness, or non-uniform thickness, (e.g., t as shown in FIG. 3). Thethickness of the first shape may, for example, be based on jaw size orcrown height, crown height being the dimension of a tooth measured fromthe junction between the enamel of the crown and the dentine of theroots, to the occlusal surface, as will be understood by one havingordinary skill in the art. For instance, a thicker first shape mayprovide more material, e.g., greater volume, to thermoform over a largerjaw size, e.g., larger dentition molds. For example, relatively largerdental appliances can also be provided with a thicker first shape 343,since the first shape 343 may be stretched more in forming a largersized dental appliance relative to a smaller size dental appliance.

Non-uniform thickness can, for example, be utilized to provide a moreuniform final thickness to a dental appliance, as in some instances, thethickness of the material may change as the appliance is formed.Accordingly, sections that typically get thinner during formation of thedental appliance, can be provided with an extra thickness duringformation of the first shape 343. In some embodiments, extra thicknesscan be used to reinforce some areas of the appliance. For example, insome areas, the extra thickness can be used to provide extra forceand/or rigidity to a particular area of the appliance.

Non-uniform thickness can, for example, vary in the range of 10-30 mil.;however, embodiments of the present disclosure are not limited to thisrange, and thickness may vary more, or less, than the above-mentionedrange. According to one or more embodiments, a green phase first sheetis fabricated to include a non-uniform thickness across the first sheetin the range of 20-30 mil., the thickness at any particular point on thefirst sheet such that after forming the dental appliance has a uniformthickness of 20 mil.

To achieve uniform thickness after forming and curing, areas of thefirst sheet that will be subject to stretching and/or thinning bybending during forming of the dental appliance over a mold may befabricated to have a greater thickness than areas of the first sheetthat will not be subject to such localized forming forces. The readerwill appreciate, that areas of the first sheet corresponding totransitions during forming into a final dental appliance, can be formedto have a greater thickness in the first sheet to accommodate the changein thickness during the forming transition.

The first sheet can be fabricated to have non-uniform thickness, suchthat a dental appliance formed from the first sheet having thenon-uniform thickness, will also have non-uniform thickness. Forexample, it may be desired to have an occlusal area of a dentalappliance (after forming) to have a different thickness than a gingivalarea of the dental appliance. It may also be desired, depending on theforces needed to move particular teeth, to have one area of the dentalappliance have a different thickness than another area of the dentalappliance. These areas of different thickness in the final dentalappliance may be achieved, at least in part, by forming the dentalappliance using a green phase first sheet fabricated to have anon-uniform thickness across the first sheet (e.g., the first sheetbeing thicker in areas corresponding to areas of the dental appliancedesired to have greater thickness).

Computer analysis may be used to model such material forces duringformation from the first sheet (e.g., green phase) to the final dentalappliance, for example, by using a computer system such as thatillustrated in FIG. 9. Computer modeling and analysis may also be usedto predict forces used to achieve desired tooth movement over a courseof treatment, and how dental appliance material thickness impacts thoseforces, such as uniform thickness across the dental appliance and/orlocalized variations in material thickness. A computer system may beused to simulate force, accounting for material thickness, and in doingso determine customized thickness characteristics for a particular firstsheet.

FIG. 4A illustrates an embodiment of a first shape 436 substantiallyhorseshoe-shaped in at least one dimension according to the presentdisclosure. As a patient's dentition, and the polymeric dentalappliances for orthodontic dental treatment, are generalhorseshoe-shaped in at least one dimension, by forming the first shape,e.g., 436, to be substantially horseshoe-shaped in at least onedimension can save some material, compared with a square-shaped, e.g.,sheet-like, first shape.

FIG. 4B illustrates a first shape 436 cross section as taken along line4B-4B of FIG. 4A. The cross section of first shape 436 illustrates thatthe first shape can be formed to have a non-uniform thickness. Howeverin some embodiments, a first shape that is substantiallyhorseshoe-shaped in at least one dimension can also be formed to besubstantially flat, e.g., having a constant thickness.

As one might envision first shape 436 being subsequently thermoformedonto a dentition, the reader can appreciate the location of sideportions used to form the sides of a dental appliance generally at lines438 and 440 on the first shape. The portion of the first shape 436 thatwill be formed into an occlusal surface of the dental appliance islocated generally between lines 439 and 441. The approximate location onthe first shape 436 which corresponds then to the transition from theocclusal surface to the side surfaces after thermoforming onto adentition is generally between lines 438 and 439, and between lines 440and 441 respectively.

The area between lines 438 and 440 on the first shape corresponds to thelocation at which the occlusal surface area 442 will exist afterthermoforming onto a dentition, as shown in FIGS. 4A and 4B. Thethickness of the first sheet 436 need not be uniform in cross section atlines 438 and 440 with respect to the occlusal surface area 442. Thethickness of a first shape can vary across its cross section.

The material in some areas of the first shape may be stretched furtherin forming a dental appliance; therefore, in some instances it can bebeneficial to have a greater quantity of thermoset polymer material withwhich to use in stretching in particular areas of the first shape. For afixed area of the first shape, and given a constant density of thermosetpolymer material, a greater quantity of thermoset polymer materialcorresponds to a greater thickness in the fixed area.

One skilled in the art will appreciate then, that a thicker first shapeprovides a greater quantity of thermoset polymer material than a thinnerfirst shape having the same planar area. It will be further appreciatedthat for a larger jaw size, in order to obtain a dental appliance withthe same post-shaping thicknesses, a greater quantity of thermosetpolymer material is needed, which can be obtained by using a thickerfirst shape for a given planar area.

The thickness of the first shape can also vary such that the thermosetpolymer material has a greater thickness along the transition lines 438and 440 and/or along the side surfaces than along an occlusal surfaceafter thermoforming onto the dentition mold. The thickness of the firstshape can also vary, in one or more dimensions, such that the thermosetpolymer material has a substantially constant thickness afterthermoforming onto the dentition mold.

In some embodiments, first shapes may be made in mass quantities, andstored, or may be made on demand according to a particular patient'sneeds. The first shape may be customized to the shape of a patient'sjaw, and with variable thickness to accommodate different crown heights.

FIG. 5A illustrates an embodiment of a first shape 550 substantiallyhorseshoe-shaped in at least two dimensions according to the presentdisclosure, and FIG. 5B illustrates the first shape cross section 552 astaken along line 5B-5B of FIG. 5A. FIG. 5A shows a first shape 550 usedto form a dental appliance that will correspond to a negative dentitionmold of the intended configuration 504.

From FIGS. 5A and 5B, it can be seen that the first shape 550 is formedto be substantially horseshoe-shaped in a first dimension, similar tofirst shape 436 shown in FIG. 4A. First shape 550 also has asubstantially horseshoe-shaped cross section, e.g., be substantiallyhorseshoe-shaped in a second dimension, as can be appreciated from FIG.5B. Thus, first shape 550 has a substantially horseshoe-shaped crosssection 552 along its substantially horseshoe-shape in a firstdimension. Lines 538, 539, 540 and 541 shown in FIG. 5B on cross-section552 correspond in location respectively to lines 438, 439, 440 and 441shown on first shape 436 in FIGS. 4A and 4B.

FIG. 6 illustrates an embodiment of a first shape 670 having a variablethickness according to the present disclosure. It can be beneficial insome instances to apply force to move teeth at a particular locationclose to the root. Therefore in such instances, it can be beneficial fora polymeric dental appliance for orthodontic dental treatment to bethicker along a gingival line, in order to provide more materialstiffness, and thus more force. It can also be beneficial in someembodiments for a polymeric dental appliance for orthodontic dentaltreatment to be thinner at the occlusal surface, for example, tominimize the gap created in bite between the jaws when the dentalappliance is in place.

The thickness, e.g., 672, of a first shape 670 can vary independentlyalong one or more dimensions, e.g., width 676 and/or length 678. Firstshape can have one or more flat surfaces, e.g., on a bottom surface 680and or a top surface 682. Furthermore, the first shape may be formed tohave a thickness that varies such that the thermoset polymer materialhas a greater thickness 672 at locations corresponding to where thegingival lines will be formed, than the thickness 674 corresponding towhere an occlusal surface will be formed.

For example, first shape 670 may be formed to have a channel, or groove,within a top surface 682 (as shown) and/or a bottom surface. The channelcan, for example, substantially follow a horse-shoe shape of thedentition onto which it may be thermoformed, and may be any suitablecross-section (e.g., semi-circular as shown in FIG. 9).

FIG. 7 illustrates working range curves of displacement as a function ofstatic force for thermoset polymer material in contrast to thermoplasticmaterial. As will be appreciated, the displacement of thermoset polymermaterial is generally within a narrower range for a given magnitude ofstatic force, than are expected for thermoplastic material.

That is, that the range of deformation for thermoset polymer material isgenerally less at a particular applied force, than the range ofdeformation for thermoplastic material at the same particular appliedforce, as can be seen by the narrower horizontal width bounded by eachcurve at the particular applied force. A smaller deformation range canhelp provide more precise, and thus controllable, locating of teethpositioning.

FIG. 8 illustrates stress relaxation performance curves of percentage ofload remaining as a function of time for thermoset polymer material(e.g., casting polyurethane) in contrast to thermoplastic material(e.g., polyester, thermoplastic polyurethane). FIG. 8 illustratesthermoset polymer material and thermoplastic material response torelaxation of stress when tested at five percent (5%) strain, atemperature of 37° C., and one hundred percent (100%) relative humidity.As may be observed, the thermoset polymer material exhibits a greaterpercentage of load remaining over time, indicating less susceptibilityto fatigue of the thermoset polymer material as compared to thethermoplastic material.

FIG. 9 illustrates a computing device embodiment to perform a method forevaluating a dental condition according to an embodiment of the presentdisclosure. The computing device 984 illustrated in FIG. 9, includes aprocessor 985 and memory 986. Memory 986 can include various types ofinformation including data 987 and computing device executableinstructions 988 as discussed herein.

Memory can be used for a variety of different functions in the variousembodiments. For example, memory can be used to store executableinstructions that can be used to interact with the other components ofthe computing device and/or network including other computing devicesand can be used to store information, such as instructions formanipulating one or more files.

For instance, in some embodiments, a computing device can includeexecutable instructions for saving a number of program and/or datafiles, such as files, for providing executable instructions that allowfor the viewing functionality for viewing scans and/or models, and thedata files for the scans and/or digital models. Some executableinstructions can, for example, be instructions for saving local scansand/or digital models, scans and/or digital models from anothercomputing device on the network, or a combination of two or more ofthese.

Additionally, as illustrated in the embodiment of FIG. 9, a system caninclude a network interface 990. Such an interface can allow forprocessing on one or more networked computing devices or such devicescan be used to transmit and/or receive scans and/or digital modelsand/or executable instructions for use with various embodiments providedherein.

The network interface 990 can connect the computing device to a network991. The network 991 can be connected to other computing devices thatcan execute to make scans and/or digital models of a patient's teeth.

For example, the digital model obtained from a scanner that isinterfaced with computing device 984 can be sent on the network 991 toother computing devices. In some embodiments, a number of treatmentprofessionals can have access to the computing devices on the network991 so they can view and diagnose the dental condition of a user basedon the digital model from a remote location.

In the embodiment of FIG. 9, the network 991 is connected to a database998. The database 998 can, for example, include a case history databasethat can give access to prior patient's data or other data resources touse in the evaluation and/or treatment process. In such embodiments,treatment professionals that have access to the network 991 and in turnthe database 998 can use the database to supplement their evaluationand/or treatment of a user's dental condition.

In some embodiments, the computing device 984 can include executableinstructions for estimating the thickness of various portions of thepartially cured material. For example, executable instructions can beprovided to adjust the thickness of the partially cured material inorder to compensate for bending or stretching that may occur duringformation of the dental appliance. The data regarding the bending and/orstretching for such analysis can be provided, for example, in memory 986and/or database 998.

As illustrated in the embodiment of FIG. 9, a system can include one ormore input and/or output interfaces 992. Such interfaces can be used toconnect the computing device with one or more input and/or outputdevices.

Such connectivity on the network 991 can allow for the input and/oroutput of manipulations (e.g., changes to the common file embedded inexecutable instructions) among other types of information. Although someembodiments may be distributed among various computing devices withinone or more networks, such systems as illustrated in FIG. 9, can bebeneficial in allowing for the capture, calculation, and/or analysis ofthe various information discussed herein. For example, the informationregarding the adjustment of the thickness of the partially curedmaterial can be provided to a device that is forming the partially curedmaterial, such as via the output interface 992.

Various embodiments include the use of executable instructions toaccomplish one or more processes. Such instructions can, for example, beimplemented on one or more computing devices and therefore in suchembodiments, the executable instructions should be viewed as beingcomputing device executable instructions for implementation by one ormore computing devices.

Although specific embodiments have been illustrated and describedherein, those of ordinary skill in the art will appreciate that anyarrangement calculated to achieve the same techniques can be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments of thedisclosure.

It is to be understood that the use of the terms “a”, “an”, “one ormore”, “a number of”, or “at least one” are all to be interpreted asmeaning one or more of an item is present. Additionally, it is to beunderstood that the above description has been made in an illustrativefashion, and not a restrictive one. Combination of the aboveembodiments, and other embodiments not specifically described hereinwill be apparent to those of skill in the art upon reviewing the abovedescription.

The scope of the various embodiments of the disclosure includes anyother applications in which the above structures and methods are used.Therefore, the scope of various embodiments of the disclosure should bedetermined with reference to the appended claims, along with the fullrange of equivalents to which such claims are entitled.

In the foregoing Detailed Description, various features are groupedtogether in a single embodiment for the purpose of streamlining thedisclosure. This method of disclosure is not to be interpreted asreflecting an intention that the embodiments of the disclosure requiremore features than are expressly recited in each claim.

Rather, as the following claims reflect, inventive subject matter liesin less than all features of a single disclosed embodiment. Thus, thefollowing claims are hereby incorporated into the Detailed Description,with each claim standing on its own as a separate embodiment.

What is claimed:
 1. A method for forming a dental appliance, comprising:partially curing a thermoset polymer material into a semi-solid formablefirst shape in a first mold; removing the semi-solid formable firstshape from the first mold; thermoforming the semi-solid formable firstshape of thermoset polymer material onto a dentition mold, wherein thefirst mold is a different mold than the dentition mold; and fullycuring, by application of heat, the thermoset polymer on the dentitionmold to complete a molecular cross-linking reaction to form the dentalappliance, wherein the dental appliance is a shell having a number ofcavities to receive one or more teeth.
 2. The method of claim 1, whereincuring the thermoset polymer on the dentition mold includes adding acurative trigger to complete the molecular cross-linking reaction. 3.The method of claim 2, wherein the curative trigger is energy.
 4. Themethod of claim 1, wherein the dental appliance is formed by a processselected from the group including molding, extrusion, and rolling. 5.The method of claim 1, wherein the forming is accomplished by a processselected from the group including compression molding, liquid injectionmolding, or reaction injection molding.
 6. The method of claim 1,wherein the semi-solid formable first shape is substantiallyhorseshoe-shaped in at least one dimension, having proportions at leastas large as a top view of the dentition mold.
 7. The method of claim 1,wherein the semi-solid formable first shape is substantiallyhorseshoe-shaped in at least two dimensions.
 8. The method of claim 1,wherein the semi-solid formable first shape has a uniform thickness. 9.The method of claim 1, wherein the semi-solid formable first shape has athickness based on jaw size.
 10. The method of claim 1, wherein thesemi-solid formable first shape has a thickness based on a crown height.11. The method of claim 1, wherein the semi-solid formable first shapehas a non-uniform thickness.
 12. The method of claim 11, whereinthickness of the semi-solid formable first shape varies such that thethermoset polymer material has a greater thickness along a gingival linethan along an occlusal surface after thermoforming onto the dentitionmold.
 13. The method of claim 11, wherein thickness of the semi-solidformable first shape varies such that the thermoset polymer material hasa substantially uniform thickness after thermoforming onto the dentitionmold.
 14. The method of claim 11, further comprising partially curingthe thermoset polymer material in the semi-solid formable first shapeprior to thermoforming.
 15. A method for forming a dental appliance,comprising: delivering a fluid thermoset polymer precursor to a firstmold; partially curing the thermoset polymer precursor in the first moldinto a semi-solid formable first shape; removing the partially curedsemi-solid formable first shape from the first mold; thermoforming thepartially cured semi-solid formable first shape of thermoset polymerprecursor onto a dentition mold; and curing, by application of heat, thethermoset polymer precursor on the dentition mold to induce across-linking reaction to form the dental appliance, wherein the dentalappliance is a shell having a number of cavities to receive one or moreteeth.
 16. The method of claim 15, wherein curing the thermoset polymerprecursor on the dentition mold includes adding a curative trigger toinduce the cross-linking reaction.
 17. The method of claim 16, whereinthe curative trigger is energy.
 18. The method of claim 17, wherein theenergy to induce the cross-linking reaction is selected from the groupincluding light, radiation, and heat.
 19. The method of claim 15,wherein the first mold is configured to form the semi-solid formablefirst shape includes forming the partially cured thermoset polymerprecursor into a flat sheet.
 20. A method for forming a dentalpositioning appliance, comprising: delivering a fluid thermoset polymerprecursor to a first mold having an internal cavity, the internal cavityhaving a surface corresponding to an external surface of the dentalpositioning appliance; partially curing the fluid thermoset polymerprecursor in the first mold into a semi-solid formable first shape;placing a second mold in proximity to the first mold such that a volumefor the fluid thermoset polymer precursor remains there between, thesecond mold being a positive dentition mold having an external surfacecorresponding to an internal surface of the dental positioningappliance; and curing the fluid thermoset polymer precursor to causemolecules of the fluid thermoset polymer precursor to irreversiblycross-link into a rigid three dimensional structure to form the dentalpositioning appliance, wherein the dental positioning appliance is ashell having a number of cavities to receive one or more teeth.
 21. Themethod of claim 20, wherein curing the thermoset polymer precursorincludes adding a curative trigger to cause molecules of the fluidthermoset polymer precursor to irreversibly cross-link into a rigidthree dimensional structure.
 22. The method of claim 21, wherein thecurative trigger is energy.
 23. The method of claim 20, where the fluidthermoset polymer precursor includes two or more prepolymer componentsand at least one curative to initiate a chemical reaction involving thetwo or more components.
 24. The method of claim 23, where the fluidthermoset polymer precursor includes at least one or more isocyanates,one or more polyols, and a curative.